Safety lock for a linear fluid pressure actuator

ABSTRACT

A rigid, elongated spacer of generally U-shaped cross-section adapted to fit over the extended piston rod of a hydraulic ram and having opposite ends engageable with the cylinder body and outer end of the rod, respectively, to prevent retraction of the latter. The spacer is pivotally mounted on the outer end of the rod for swinging movement between its operative position and an inoperative position. A removable pin acts to releasably maintain the spacer in the former position.

United States Patent Carlson et al.

[ 51 3,662,653 1 May 16,1972

[54] SAFETY LOCK FOR A LINEAR FLUID PRESSURE ACTUATOR [72] Inventors: Robert Philip Carlson, Bettendorf, Iowa; George Frederick Oelschlaeger, Rock Island, 111.

[73] Assignee: Deere & Company, Moline, Ill.

[22] Filed: Mar. 26, 1970 [21] Appl. No.: 22,922

[52] U.S. Cl .'...92/l5, 74/527, 188/67 [51] Int. Cl ..Fl5b 15/26 [58] Field of Search ..92/l5, 17, 14, 20, 22, 23;

[56] References Cited UNITED STATES PATENTS Voight ..92/15 X Bommer ..16/51 X 2,274,668 3/1942 Crawford et al. ..92/l X 2,516,480 7/1950 OShei ..74/527 X FOREIGN PATENTS OR APPLICATIONS 577,947 6/1946 Great Britain ..92/ l 4 Primary Examiner-Martin P. Sehwadron Assistant ExaminerLeslie .I. Payne Attorney-H. Vincent Harsha, Harold M. Knoth, William A. Murray and John M. Nolan [57] ABSTRACT A rigid, elongated spacer of generally U-shaped cross-section adapted to fit over the extended piston rod of a hydraulic ram and having opposite ends engageable with the cylinder body and outer end of the rod, respectively, to prevent retraction of the latter. The spacer is pivotally mounted on the outer end of the rod for swinging movement between its operative position and an inoperative position. A removable pin acts to releasably maintain the spacer in the former position.

4 Claims, 4 Drawing Figures WENTEB AY 16 m2 D ID INVENTOR. ROBERT P. CARLSON GEORGE F. OELSCHLAEGER SAFETY LOCK FOR A LINEAR FLUID PRESSURE ACTUATOR BACKGROUND OF THE INVENTION The present invention relates generally to a linear fluid pressure actuator of the type comprising a cylinder and piston reciprocable therein, and more particularly to a safety device for locking the piston rod of such an actuator in its extended position.

In certain hydraulic ram applications, it is desirable for reasons of safety to provide means whereby the piston rod thereof can be positively locked in an extended position to prevent its retraction in the event of a sudden loss of fluid line pressure. The present invention, for example, finds particular utility in conjunction with a hydraulic ram used to raise and lower an agricultural implement. It is customary in the design of pull-type implements to mount the ground wheels on arms fixed to a rockshaft, and to rotate the rockshaft for raising and lowering the implement by means of a hydraulic ram. When the implement is raised for transport purposes, the piston rod is normally fully extended, and it is desirable, for the reasons noted, to provide means independent of the fluid pressure supply for preventing accidental retraction of the rod.

Locking devices for fluid pressure actuators are well known in the art and are found in various forms. One class of such mechanism, exemplified by U. S. Pat. Nos. 2,764,132 to Bakke and 2,81 1,951 to Bodem et al., operates internally, while another class, to which the present invention belongs, operates externally. Examples of devices belonging to the latter class are found in U. S. Pat. Nos. 2,258,825 to Thompson 2,442,306 to McCormick and 3,135,555 to McCaskey.

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide an improved device of the class described, and more particularly such a device that is reliable, convenient to operate, and inexpensive to manufacture. These and other objects are ac complished, according to the invention, by the provision of a rigid, elongated spacer adapted to fit between the cylinder body and outer end of the extended piston rod, and having opposite ends engageable with said body and rod to prevent retraction of the latter. The spacer is releasably retained in its operative position adjacent the piston rod, and is pivotally mounted directly on the piston rod end for swinging movement to an inoperative position. The pivotal mounting includes an arm fixed to the spacer and having an elongated aperture therein receiving a mounting pin on the piston rod end. The aperture permits the spacer to move slightly relative to the pin in the direction of elongation thereof, thereby permitting the spacer to be swung past the corner of the piston rod end between its alternate positions, and assuring that no load is imposed on the arm when the spacer is disposed in its locking position.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the invention will be described in conjunction with the accompanying drawings:

FIG. 1 is a side view of a hydraulic ram incorporating the locking device of the present invention, with the piston rod extended and the locking device in its operative position.

FIG. 2 is a view similar to FIG. 1, with the piston rod retracted and the locking device in its inoperative position.

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.

FIG. 4 is a view taken along the line 4-4 of DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is illustrated in conjunction with a hydraulic ram having a cylinder body 10 including a cylinder 12 and a pair of end closure members 14 and 16. Four elongated bolts 18, evenly spaced about the circumference of the cylinder 12, extend through each of the end members 14 and 16 and threadably receive nuts 20 to hold the members on the ends of the cylinder. The cylinder 12 contains a piston (not shown) axially movable therein in response to fluid flow through the ports 22 and 24 in the end members 14 and 16, respectively. A fluid pressure supply and control system of conventional design (not shown) may be utilized to actuate the ram. A piston rod 26 is fixed to the piston and extends axially through the end member 16, the rod being shown in its extended and retracted positions in FIGS. 1 and 2, respectively. Fixed to the outer end of the rod 26 is an enlarged U-shaped connecting member or clevis 28 having suitably apertured legs 30 and 32 for receiving a cylindrical mounting pin 34. The portion of the pin 34 extending between the legs 30 and 32 pivotally receives a mounting structure 36. The pin 34 is restrained from axial movement relative to the member or clevis 28 by means of an enlarged head portion 38 formed on one of its ends and a removable retaining pin 40 received by its apertured opposite end. An anchor member 42, formed integrally with the end member 14, is pivotally mounted on a pin 44 received by a bracket 46.

The lock device of the present invention includes a rigid, elongated spacer 48 having a generally U-shaped cross-section adapted, as shown in FIGS. 1 and 3, to closely fit the extended piston rod 26. When disposed in its operative position on the rod, the opposite ends of the spacer are engageable respectively, with the cylinder end member 16 and the connecting member 28. Thus, the member 16 serves as an abutment for the cylinder body 10 that engages spacer 48. A pair of arms 50 and 52 are welded, or otherwise rigidly fixed to the sides of the outer end portion of the spacer and extend along and slightly outwardly of the legs of the member 28. The outer ends of the arms 50 and 52 are provided with elongated apertures or slots 54 and 56, respectively, for pivotally receiving the outer ends of the mounting pin 34. The spacer is thus swingable between its operative position, shown in FIGS. 1 and 3, and its inoperative position shown in FIG. 2. The slots 54 and 56, elongated as shown along the longitudinal axis of the spacer, permit limited movement of the spacer 48 relative to the pin 34 in the direction of elongation of the spacer, and thereby permit the outer end of the spacer to clear the adjacent upper corner of the member 28 as it is swung between the two positions, yet fit closely against the member when disposed in the operative position. In addition, the slots 54 and 56 assure that no load will be imposed on the arms 50 and 52 when the spacer is disposed in its operative position on the rod since the spacer, when in that position, is between the extremes of its movement relative to the pin. As shown clearly in FIG. 1, wherein the spacer is illustrated in its operative position, the pin 34 is approximately midway between the inner and outer edges of the'slots 54 and 56. A removable pin 58 extends through a pair of transversely aligned holes in the legs of the inner end portion of the spacer below the piston rod 26 to provide a latching means releasably maintaining the spacer in its operative position.

We claim:

1. For use in combination with a hydraulic ram having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, a clevis on the outer end of said piston rod, and a connecting pin extending between the legs of said clevis and having portions extending outwardly from the outer sides of said legs, a device for preventing retraction of the piston rod from its extended position comprising: a rigid, elongated spacer of generally U- shaped cross-section adapted to fit over the extended piston rod and having inner and outer ends engageable, respectively, with said cylinder body and said clevis, said spacer having a bight portion normally disposed adjacent to the piston rod, and a pair of generally parallel sides extending on opposite sides of said rod; and means for mounting said spacer on said clevis for swinging movement to an inoperative position away from said piston rod including a pair of arms fixed to the sides of said spacer and extending along opposite outer sides of said clevis, said arms having apertures therein receiving the portions of said pin extending outwardly from said clevis, said apertures being larger than said pin to permit limited movement of said spacer relative to said clevis in the direction of elongation of the spacer, said spacer being disposed between its extremes of movement relative to said clevis when the outer end of said spacer is engaged with said clevis.

2. For use in combination with a linear fluid pressure actuator having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, and a connecting member on the other end of said piston rod, a lock device comprising: a rigid, elongated spacer having a generally U-shaped cross-sectional configuration; means for swingably mounting said spacer on said connecting member for movement between operative and inoperative positions, said spacer, in its operative position, having a bight portion disposed closely adjacent to the piston rod and side portions extending on opposite sides of said rod, said spacer further having inner and outer end portions engageable in the operative position withsaid one end of said cylinder body and said connecting member, respectively, to prevent retraction of said piston rod; and means for releasably maintaining said spacer in its operative position including a pin removably received by and extending between the side portions of said spacer said 'pin being engageable with said piston rod to maintain said spacer in its operative position.

3. For use in combination with a linear fluid pressure actuator having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, a connecting member on the outer end of said piston rod, and a mounting pin received by said connecting member for connecting said member to a mounting structure, said pin including end portions extending from opposite sides of said member, a lock device comprising: a rigid, elongated spacer having a generally U shaped cross-sectional configuration; and means for swingably mounting said spacer on said mounting pin for movement between operative and inoperative positions, said spacer in its operative position having a bight portion disposed closely adjacent to the piston rod and side portions extending on opposite sides of said rod, said spacer further having inner and outer end portions engageable in the operative position with said one end of said cylinder body and said connecting member, respectively, to prevent retraction of said piston rod, said means for swingably mounting said spacer on said mounting pin including a pair of arms fixed to the side portions of said spacer and extending along the sides of said connecting member, said arms having apertures therein elongated in the direction of elongation of said spacer for receiving the end portions of said mounting pin.

4. The invention defined in claim 3 including a retaining pin removably received by and extending between the side portions of said spacer, said retaining pin being engageable with said piston rod to maintain said spacer in its operative position. 

1. For use in combination with a hydraulic ram having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, a clevis on the outer end of said piston rod, and a connecting pin extending between the legs of said clevis and having portions extending outwardly from the outer sides of said legs, a device for preventing retraction of the piston rod from its extended position comprising: a rigid, elongated spacer of generally U-shaped cross-section adapted to fit over the extended piston rod and having inner and outer ends engageable, respectively, with said cylinder body and said clevis, said spacer having a bight portion normally disposed adjacent to the piston rod, and a pair of generally parallel sides extending on opposite sides of said rod; and means for mounting said spacer on said clevis for swinging movement to an inoperative position away from said piston rod including a pair of arms fixed to the sides of said spacer and extending along opposite outer sides of said clevis, said arms having apertures therein receiving the portions of said pin extending outwardly from said clevis, said apertures being larger than said pin to permit limited movement of said spacer relative to said clevis in the direction of elongation of the spacer, said spacer being disposed between its extremes of movement relative to said clevis when the outer end of said spacer is engaged with said clevis.
 2. For use in combination with a linear fluid pressure actuator having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, and a connecting member on the other end of said piston rod, a lock device comprising: a rigid, elongated spacer having a generally U-shaped cross-sectional configuration; means for swingably mounting said spacer on said connecting member for movement between operative and inoperative positions, said spacer, in its operative position, having a bight portion disposed closely adjacent to the piston rod and side portions extending on opposite sides of said rod, said spacer further having inner and outer end portions engageable in the operative position with said one end of said cylinder body and said connecting member, respectively, to prevent retraction of said piston rod; and means for releasably maintaining said spacer in its operative position including a pin removably received by and extending between the side portions of said spacer said pin being engageable with said piston rod to maintain said spacer in its operative position.
 3. For use in combination with a linear fluid pressure actuator having a cylinder body, a piston rod extendable and retractable through one end of said cylinder body, a connecting member on the outer end of said piston rod, and a mounting pin received by said connecting member for connecting said member to a mounting structure, said pin including end portions extending from opposite sides of said member, a lock device comprising: a rigid, elongated spacer having a generally U-shaped cross-sectional configuration; and means for swingably mounting said spacer on said mounting pin for movement between operative and inoperative positions, said spacer in its operative position having a bight portion disposed closely adjacent to the piston rod and side portions extending on opposite sides of said rod, said spacer further having inner and outer end portions engageable in the operative position with said one end of said cylinder body and said connecting member, respectively, to prevent retraction of said piston rod, said means for swingably mounting said spacer on said mounting pin including a pair of arms fixed to the side portions of said spacer and extending along the sides of said connecting member, said arms having apertures therein eloNgated in the direction of elongation of said spacer for receiving the end portions of said mounting pin.
 4. The invention defined in claim 3 including a retaining pin removably received by and extending between the side portions of said spacer, said retaining pin being engageable with said piston rod to maintain said spacer in its operative position. 